JP2009041460A - Fuel injection control system for spark-ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of abnormal combustion in an internal combustion engine performing quick start at high temperature. <P>SOLUTION: It is determined whether or not a stop position of a piston in start of an internal combustion engine in each cylinder is in a period T2 after the start of an intake period Ts and before an approximately 90° ATDC of an intake TDC. Further, it is determined whether or not a cylinder temperature of a cylinder of which the stop position of the piston is in the period T2 is higher than a specified value, from an atmospheric temperature, an engine water temperature, and an elapsed time from the stop of the internal combustion engine until a restart condition is satisfied. When the stop position of the piston is in the period T2 and if it is estimated that the cylinder temperature is higher than the specific value, the fuel is injected in a plurality of times in a fuel injection period F2 in the period T2, in cranking. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection control system for a spark ignition type internal combustion engine.

In recent years, vehicles that employ an idling stop mechanism have been proposed in various forms for the purpose of reducing exhaust gas and improving fuel efficiency because of concern for environmental problems. For example, in a direct injection internal combustion engine that employs an idling stop mechanism, a cylinder that is in the compression stroke while the internal combustion engine is stopped, and a cylinder that is next in the compression stroke in order to ensure engine start performance at the time of restart An automatic stop and start device for a direct injection internal combustion engine has been proposed that injects fuel into a cylinder and then injects fuel into a cylinder in the intake stroke when a restart condition is satisfied (see Patent Document 1).
JP 2004-036561 A

  When fuel is injected into a cylinder in the intake stroke for the purpose of early start, it is necessary to inject fuel substantially simultaneously with engine rotation. However, in an eco-run system that frequently performs idling stop, the water temperature and the atmospheric temperature are often high at the time of starting, and in the cylinder in the intake stroke that does not include the exhaust stroke until the fuel injection after engine rotation, the air in the cylinder The temperature may rise and cause abnormal combustion such as pre-ignition.

  An object of the present invention is to prevent the occurrence of abnormal combustion in an internal combustion engine that starts early at a high temperature.

  In the fuel injection control system for a spark ignition type internal combustion engine of the present invention, the stop position of the piston at the start of the internal combustion engine is after the intake valve opening and before the intake stroke of approximately 90 ° ATDC. In the cylinder, fuel is injected in a plurality of times within a period from when the intake valve is opened to approximately 90 ° ATDC of the intake stroke.

  In addition, in order to perform the fuel injection control more accurately taking the correspondence with the abnormal combustion, the fuel injection divided into a plurality of times is performed on the condition that the in-cylinder temperature is estimated to be higher than the specified value. Is preferred. In particular, when the internal combustion engine is controlled based on the idling stop function, for example, an elapsed time from when the internal combustion engine is stopped to when the restart condition is satisfied is used to estimate whether the in-cylinder temperature is higher than a specified value.

  In addition, the present invention exhibits a particularly remarkable effect when fuel injection is performed at the intake port.

  As described above, according to the present invention, it is possible to prevent the occurrence of abnormal combustion in an internal combustion engine that starts early at a high temperature.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram schematically showing the configuration of an internal combustion engine according to an embodiment of the present invention. Note that FIG. 1 shows only a schematic partial sectional view of one cylinder, but the internal combustion engine includes a plurality of cylinders as conventionally known. The internal combustion engine is used in a vehicle having an idling stop function, for example.

  The cylinder block 11 of the internal combustion engine 10 is provided with a plurality of cylinder bores 13 in which pistons 12 are arranged, and the upper part thereof is covered with a cylinder head 14. The cylinder head 14 is provided with an intake port 15 and an exhaust port 16 communicating with each cylinder bore 13, an intake valve 17 is provided on the intake port 15, and an exhaust valve 18 is provided on the exhaust port 16.

  In the cylinder head 14, a spark plug 19 for spark ignition is provided at a position that forms the substantially central top surface of the combustion chamber, and an injector 20 is provided in the intake port 15. Fuel injection from the injector 20 is controlled by the ECU 21, and signals are input to the ECU 21 from various sensors (not shown). The sensor input includes, for example, an input from a temperature sensor that measures the ambient temperature and the engine water temperature, an input from a crank angle detection sensor, or an input from a timer that measures an elapsed time from the stop of the internal combustion engine.

Next, the principle of the fuel injection control process of this embodiment will be described with reference to FIG.
FIG. 2 is a timing chart showing the timing of fuel injection at the time of restart after the internal combustion engine is stopped in the idling stop control.

  FIG. 2 shows an intake period Ts in which the intake valve 17 is opened and an exhaust period Te in which the exhaust valve 18 is opened. As is well known in the art, the intake period Ts is a period from before the TDC of the intake stroke to the hit after passing the BDC of the intake stroke, and the exhaust period Te is a hit from before the BDC of the exhaust stroke and after the intake TDC. The period until. In FIG. 2, the ignition timing P is a target ignition timing at the time of restart, and in order to ignite at the ignition timing P, fuel is injected from the injector 20 into the intake port 15 by approximately 90 ° ATDC of the intake stroke. Must be done (within period T0).

  For example, when the position of the piston when the internal combustion engine is stopped is in the period T1 before the intake valve 17 is opened, the fuel can be injected in the fuel injection period F1 immediately before the intake valve 17 is opened. In such a case, when the crankshaft is rotated in the restart, the air after the fuel mixing at the intake port 15 is sucked into the cylinder, so that the homogeneity is sufficiently maintained. In such a case, since at least a part of the exhaust stroke is included in the period up to the ignition timing P, the high-temperature air in the cylinder is discharged, and the low-temperature air in the surge tank is supplied to the cylinder.

  That is, in the case where the position of the piston when the internal combustion engine is stopped is in the period T1, if the fuel is injected once in the fuel injection period F1, it is possible to perform underignition with sufficient homogeneity and relatively low in-cylinder temperature. Therefore, it does not cause abnormal combustion.

  On the other hand, when the position of the piston when the internal combustion engine is stopped is after the opening of the intake valve 17 and in a period T2 up to approximately 90 ° ATDC of the intake TDC, fuel is injected almost simultaneously with the rotation of the crankshaft. There is a need to. At this time, if fuel injection is performed once in the period T2 (fuel injection period F1 ') as in the case of the cylinder in which the position of the piston when the internal combustion engine is stopped is in the period T1, abnormal combustion occurs.

  That is, when the position of the piston when the internal combustion engine is stopped is in the period T2, the exhaust stroke is hardly included until the ignition timing P. Therefore, when the time has not passed much after the internal combustion engine has stopped, the high water temperature and the high Air heated by the ambient temperature remains in the cylinder, and combustion is performed at a high temperature. Further, since the fuel injection at this time is the intake stroke injection, the homogeneity of the air-fuel mixture deteriorates. That is, when the position of the piston when the internal combustion engine is stopped is in the period T2, if one fuel injection is performed in the fuel injection period F1 ′, the air-fuel mixture with low homogeneity is burned at a high temperature, causing abnormal combustion. Probability is high.

  Therefore, in this embodiment, when the position of the piston when the internal combustion engine is stopped is in the period T2, in the fuel injection period F2 in the period T2, the fuel is divided and injected (multi-injection) multiple times. Increases the homogeneity of gas and prevents the occurrence of abnormal combustion.

  Next, the flow of the fuel injection control process of the present embodiment will be described with reference to the flowchart of FIG. The fuel injection control process shown in FIG. 3 is executed in the ECU 21 when the restart condition is satisfied after the internal combustion engine is stopped by idling stop. The restart condition is, for example, detection of brake release.

  In step S100, the crank angle CA at the internal combustion engine stop position is detected. In steps S102, S104, and S106, the ambient temperature TA, the engine water temperature TW, and the elapsed time TD from the stop of the internal combustion engine are detected.

  In step S108, it is determined whether or not to perform multi-injection for each cylinder. That is, it is determined whether or not the detected crank angle CA is a position after the intake valve opening or after the intake TDC in each cylinder and before the 90 ° ATDC of the intake TDC. Furthermore, for example, it is determined whether or not the ambient temperature TA and the engine water temperature TW are larger than the respective prescribed values, and whether the elapsed time TD after the internal combustion engine is stopped is shorter than the prescribed value, and the cylinder interior at the time of restart is determined. It is estimated whether or not the mixture temperature is in a state that requires multi-injection.

  In step S108, the detected crank angle CA is a position after the intake valve is opened or after the intake TDC and before the 90 ° ATDC of the intake TDC, and the ambient temperature TA and the engine water temperature TW are specified values. For a cylinder that is larger than the specified value and the elapsed time TD after the stop of the internal combustion engine is shorter than the specified value, the multi-injection execution flag F is set in step S110 (F = 1). On the other hand, in step S108, the multi-injection execution flag F is cleared (F = 0) in step S112 for cylinders for which any of the above conditions is not satisfied.

  In step S114, cranking is started, and in step S116, it is determined whether or not the multi-injection flag F of each cylinder is set. For cylinders for which the multi-injection flag F is set (F = 1), multi-injection is executed in step S118, and for cylinders for which the multi-injection flag F is not set (F = 0), step In S120, one injection is performed.

  Thus, the fuel injection control process of the present embodiment is completed, and the ECU 21 returns to normal control.

  As described above, according to the present embodiment, the homogeneity of the air-fuel mixture can be maintained high in each cylinder regardless of the crank angle, so that the vehicle can be provided at short intervals as in a vehicle having an idling stop function. Abnormal combustion can be prevented even when the internal combustion engine is stopped and restarted and early ignition at a high temperature is required.

1 is a block diagram schematically showing the configuration of an internal combustion engine that is an embodiment of the present invention. 6 is a timing chart showing the timing of fuel injection during restart after the internal combustion engine is stopped in idling stop control. It is a flowchart of a fuel injection process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Cylinder block 12 Piston 13 Cylinder bore 14 Cylinder head 15 Intake port 16 Exhaust port 17 Intake valve 18 Exhaust valve 19 Spark plug 20 Injector 21 ECU

Claims (4)

  In a cylinder where the stop position of the piston at the start of the internal combustion engine is after the intake valve opening and before the intake stroke of approximately 90 ° ATDC, the intake stroke is substantially omitted from the intake valve opening. A fuel injection control system for a spark ignition type internal combustion engine, wherein fuel is injected in a plurality of times within a period up to 90 ° ATDC.   2. The fuel injection control system according to claim 1, wherein the fuel injection divided into a plurality of times is performed on the condition that an in-cylinder temperature of the cylinder is further estimated to be higher than a specified value.   The internal combustion engine is controlled based on an idling stop function, and an elapsed time from when the internal combustion engine is stopped to when a restart condition is established is used to estimate whether the in-cylinder temperature is higher than a specified value. The fuel injection control system according to claim 2. The fuel injection control system according to claim 1, wherein fuel injection is performed at an intake port.

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